The 7×57mmcartridge, also known as the 7mm Mauser, 7×57mm Mauser, 7mm Spanish Mauser in the USA and .275 Rigby in the United Kingdom is a first-generation smokeless powderrimless bottlenecked riflecartridge. It was developed by Paul Mauser of the Mauser company in 1892 and adopted as a military cartridge by Spain in 1893.[2] It was subsequently adopted by several other countries as the standard military cartridge. It is recognised as a milestone in modern cartridge design, and although now obsolete as a military cartridge, it remains in widespread international use as a sporting round. The 7×57mm has been described as "a ballistician's delight".[citation needed] Many sporting rifles in this calibre were made by British riflemakers, among whom John Rigby was prominent; and, catering for the British preference for calibres to be designated in inches, Rigby called this chambering the .275 bore after the measurement of a 7 mm rifle's bore across the lands.[2]

Paul Mauser visited the Kingdom of Spain in 1892 after the delivery of trial rifles in 1891 and brought with him a new rifle designed to use a new cartridge of 7 mm caliber. He had developed this cartridge for use with the then-new smokeless propellant, introduced as Poudre B in the 1886 pattern 8mm Lebel, which started a military rifle ammunition revolution. At the time of its development 7×57mm Mauser was a high-performance smokeless-powder cartridge. The Mauser Model 1892 rifle turned out to be a transitional design that was manufactured in limited numbers for the Spanish Army.[3] It was quickly improved to the Mauser Model 1893 featuring a new internal box magazine where the cartridges were stored in a staggered column. The Spaniards were so impressed with the Mauser Model 1892 and 1893 rifles and their new 7×57mm Mauser cartridge that they not only ordered rifles and ammunition with Mauser, but also awarded him the Grand Cross of the Spanish Military Order of Merit, the highest decoration Mauser ever received.[4]

According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings the 7×57mm case can handle up to 390.00 MPa (56,565 psi) Pmax piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers.[5]

The SAAMI Maximum Average Pressure (MAP) for this cartridge is 51,000 psi (351.63 MPa) piezo pressure or 46,000 CUP.[6][7] Although this lower specification is in deference to the purportedly weaker actions of the older Mauser 93 and 95 rifles which are still in circulation,[7] this concern is misplaced, as the original ammunition developed for, and issued with, the M93 Spanish Mauser produced an average pressure of 50,370 CUP in those rifles.[8][9]

A rimmed cartridge was developed from the 7×57mm shortly after its introduction for use in break-action rifles and combination guns. A rimmed cartridge greatly simplifies the issues of designing an extractor, particularly in a combination gun or "drilling" which must also be designed to extract rimmed shotgun shells. While various modern break-action and single-shot rifle and pistol designs have been developed that can reliably extract rimless cartridges, most of these date from the 1970s or later.[citation needed] While the external dimensions of the two versions are nearly identical other than the rim, there are differences in the internal design. In particular, the cartridge web, the area immediately above the rim on the rimmed version or the rebate on the rimless version, is thinner in the rimmed case, and some authorities recommend limiting the rimmed cartridge to 41,000 CUP because of this.[10]

The ballistics of the 7×57mm became popular with deer and plains game hunters. The relatively flat trajectory and manageable recoil ensured its place as a sportsman's cartridge. The 7×57mm can offer very good penetrating ability due to a fast twist rate that enables it to fire long, heavy bullets with a high sectional density. This made it popular in Africa, where it was used on animals up to and including elephants, for which it was particularly favoured by noted ivory hunter W.D.M. "Karamojo" Bell, who shot about 800 African Elephants with 1893 pattern 7×57mm military ball ammunition using RigbyMauser 98 rifles, when most ivory hunters were using larger-caliber rifles.[12] Bell selected the cartridge for moderate recoil, and used 11.2-gram (172.8 gr) long round-nosed military full metal jacket bullets for reliable penetration. Bell sectioned an elephant skull to determine the size and location of the brain, and used careful aim to ensure bullet placement in the brain.[2]

The 7×57mm was also the favored cartridge of Eleanor O'Connor, wife of famous hunter and author Jack O'Connor. Eleanor accompanied her husband on multiple hunting expeditions all over the world, killing small and large game with the 7×57mm.[citation needed] Though not as popular today, the 7×57mm is still produced by most major ammunition manufacturers and many modern rifles are available chambered for the cartridge.

The 7×57mm round was also used by the Indian hunter and conservationist Jim Corbett to put down the infamous man-eating Leopard of Rudraprayag besides a few other Man-Eaters of Kumaon. Corbett's writings mention using the .275 Mauser-Rigby rifle with attached torch to despatch the leopard on a dark summer night in May 1926. For man-eating tigers, Corbett preferred a double-barrelled .450/400 Nitro Express rifle but retained the Mauser-Rigby as a backup weapon.[citation needed]

Able to handle a wide range of projectile weights, easy to reload, mild in recoil and accurate, the 7×57 offers a lot. This is well known to hunters, through both personal experience and the reading of a well-documented track record extending back more than 100 years. Rifle Metallic Silhouette shooters are also discovering the versatility and competitiveness of the 7×57.[13]

The military of the Kingdom of Spain adopted the Mauser Model 1893 rifle. It was chambered for the new 7×57mm Mauser cartridge. The original cartridge featured a long, 11.2-gram (173 gr) round-nose, full-metal-jacketed bullet with a muzzle velocity of about 700 m/s (2,300 ft/s) with 2,744 J (2,024 ft⋅lbf) muzzle energy from a 740 mm (29.1 in) barreled rifle.[2] For the late 19th century, these ballistics were impressive, and the loading provided a fairly flat trajectory combined with excellent penetration. At the same time, it exhibited relatively modest free recoil. That was a combination of attributes that made it popular with both soldiers and sportsmen alike.

The qualities of the 7×57mm as a military round were shown in the Spanish–American War of 1898. At the commencement of the American assault on the strategic Cuban city of Santiago, 750 Spanish troops defended positions on San Juan and Kettle Hills. The attacking force numbered approximately 6,600 American soldiers, most of them armed with then-new smokeless-powder Krag–Jørgensen rifle in .30-40 Krag caliber,[14] and supported by artillery and Gatling gun fire. Though the assault was successful, the Americans soon realized that they had suffered more than 1,400 casualties, nearly 20 per cent of their forces. A U.S. board of investigation later concluded that the casualties were primarily due to the superior firepower of the Spanish Model 1893 Mauser rifles.[citation needed]

During the Second Boer War in South Africa, British authorities were obliged to re-evaluate rifle and ammunition design and tactics after facing Boer sharpshooters and snipers armed with Mauser Model 1895 rifles firing 7×57mm rounds with withering effectiveness, easily outranging the .303 British cartridge as regards accurate long-range fire.[15] The .303 British cartridge at that time was still using cordite propellant, in contrast to the Mauser's higher-performance ballistite type smokeless powder.[16] The British modernized the .303 British cartridge to the Mark 7 variant with a "spitzer" bullet, and updated their rifle to the Short Magazine Lee–Enfield No. 1 Mk III.

The oldest 1893 pattern military ball ammunition was loaded with a 11.2-gram (172.8 gr) long round-nosed bullet fired at a muzzle velocity of 670 m/s (2,198 ft/s) with 2,514 J (1,854 ft⋅lbf) muzzle energy from a 589 mm (23.2 in) long barrel. It had a maximum range of 3,250 m (3,554 yd).[17] In 1893 this ballistic performance made it the high-performance service cartridge champion of its day when compared to other 1893 pattern smokeless-powder cartridges such as the 8mm Lebel, .303 British, and 8×50mmR Mannlicher.

In 1913, following the lead of French and German Army commands in developing the spitzer or pointed-tip bullet shape, the Spanish ordnance authorities issued a redesigned 7×57mm cartridge with a spitzer bullet (7mm Cartucho para Mauser Tipo S).[18] It was loaded with a 9-gram (138.9 gr) spitzer bullet fired at a muzzle velocity of 850 m/s (2,789 ft/s) with 3,251 J (2,398 ft⋅lbf) muzzle energy from a 589 mm (23.2 in) long barrel. It had a maximum range of 3,700 m (4,046 yd).[17] The new spitzer bullet style was partially responsible for the cartridge's improved performance as it significantly reduced air drag within normal combat ranges and withstood higher accelerations in the barrel.

After that military ball ammunition loaded with a 10.5-gram (162.0 gr) spitzer bullet fired at a muzzle velocity of 750 m/s (2,461 ft/s) with 2,953 J (2,178 ft⋅lbf) muzzle energy from a 589 mm (23.2 in) long barrel became available. Besides a pointed nose this projectile also had a boat tail to reduce drag. It had a maximum range of 5,000 m (5,468 yd).[17]

The 7×57mm Mauser is also used as the parent case for a host of modified variants that are not officially registered with or sanctioned by C.I.P. or its American equivalent, SAAMI. These cartridges are known as wildcat cartridges.
The US wildcat cartridge developer P.O. Ackley developed several 7×57mm Mauser based wildcat cartridges.[30]
The 7×57mm Mauser Ackley Improved is an alternate version of the 7×57mm Mauser cartridge with 40 degree shoulder. This wildcat was designed to be easily made by rechambering existing firearms, and fire forming the ammunition to decrease body taper and increase shoulder angle, resulting in a higher case capacity. Dies for this wildcat chambering are readily available.
The .228 Ackley Magnum is also based on the 7×57mm Mauser cartridge but is also necked down to .228 caliber (5.79 mm). Bullets in this caliber are hard to find but provide greater weight than .223 caliber bullets, up to 100 grains (6.5 g), without excessively quick twist rate.
The .257 Roberts Ackley Improved is a second generation wildcat cartridge based on the .257 Roberts cartridge.